1. Field of the Invention
This invention relates to a controlling apparatus for a hybrid car provided with an internal combustion engine and electric driving means.
2. Description of the Relevant Art
For an engine of a vehicle, torque and revolution number characteristics over a wide range are required so that the engine may operate in any running condition (constant speed, acceleration, uphill road running and so forth). Generally, the torque and the number of revolutions of the engine in which the fuel consumption efficiency is high are limited to a range peculiar to the engine. Therefore, there has been proposed a hybrid car wherein an engine and a generator-motor are carried on an automobile so that drawbacks of one may be made up for by the other to raise the overall energy efficiency of the car.
In a conventional hybrid car, the engine is designed with a reduced capacity and is normally operated only in a range in which it exhibits a high fuel consumption efficiency. Furthermore, a controlling apparatus for the hybrid car oversees regenerative control such that, when the car is accelerated or runs on an uphill road or the like, driving of the generator-motor is controlled with supplied power from a power supply such as a battery to make up for an insufficient driving torque. However, when the output of the engine exhibits some surplus power, generated energy obtained when the generator-motor is driven by the engine is regenerated into the power supply such as a battery.
A controlling apparatus for a conventional hybrid car wherein an operation amount of an accelerator pedal by a driver during running of the vehicle is detected by an accelerator sensor. An engine torque is calculated from a throttle opening based on the detection signal and an engine revolution number based on a signal is detected by a pulser provided on a crankshaft of an engine. Regeneration current of a motor is calculated so that, when the calculated torque is lower than a fuel consumption optimum torque upon the revolution number, the throttle opening may be increased by a difference between them and a torque corresponding to the difference may be generated to control the engine and the motor. A device of this type is disclosed in the official gazette of Japanese Patent Laid-Open Application No. Heisei 5-22931.
With the controlling apparatus for a conventional hybrid car, since a driving region of the engine and a driving region of the generator-motor in a region set in accordance with a vehicle speed and an accelerator opening are determined in advance by the controlling apparatus, a driver cannot select arbitrarily whether gasoline should be preserved or a battery should be preserved. The conventional hybrid car employs a controlling method wherein the two different power sources of the engine and the motor are combined and a driving output torque and/or a revolution number of each of the power sources are calculated. Calculation is performed based on the detected signals to compensate for a torque difference based on a result of the calculation or change over between the two different power sources depending upon the vehicle speed or the like.
In the conventional hybrid car, where the opening degree of the throttle is controlled based on a signal from the accelerator sensor and the revolution number signal of the engine to attain a torque requested by a driver, the output torque amount of the engine is different depending upon the condition in which the engine is used such as whether it is cold or hot, an individual difference of the engine and so forth, by which the linearity of the running driving torque with respect to the accelerator is damaged.
Also in the conventional hybrid car, by control based merely on signals of the accelerator sensor and the engine revolution number, the two power sources of different characteristics of the engine which has a long response time until a required torque is reached and a moderate startup is exhibited, and the motor which has a short response time and exhibits a rapid startup, the running driving force is discontinuous and lacks smoothness.
Furthermore, where a torque is to be detected from a driving power outputting element of each of the two power sources of the engine and the motor, when the use condition is cold, torque calculations for the engine which exhibits a large torque variation and the motor which exhibits a small torque variation must be processed at all times. Where torque sensors are used individually for the driving power outputting elements of the two power sources of the engine and the motor, the conventional hybrid car has an increased number of parts, an increased mounting space and so forth.